The invention is characterized in particular by the fact that the vibrations of an object are measured by distinguishing phases of low-amplitude trembling of the object from phases of greater trembling due to unwanted stimulation, so as to respond to the lowest values (trembling when resting) and eliminate the highest values. One manner of distinguishing resting trembling phases from greater amplitude trembling phases due to unwanted stimulation consists in measuring the absolute minimum of the amplitude of vibrations of an object over a predetermined period. Thus a sudden and unexpected vibration during the measurement (twitch, impact, etc) has no effect on the result.
Applications of the invention to measuring the nervous trembling of living organisms are particularly useful because the amplitude of trembling when an animal or a person is resting increases when the animal or person is irritated, tired or has consumed unnatural substances (tobacco, coffee, artificial foodstuffs, etc). Simple measurement of the amplitude of trembling is insufficient, however, because the signal generated by the sensor is the result of microscopic trembling (which is of interest) and of macroscopic muscular movements of much greater amplitude. It is not possible to distinguish trembling when resting from trembling when active (or muscular trembling) by frequency-selective filtering, as resting trembling and muscular trembling are of the same frequency, in the order of 10 Hz in man. The process and the device in accordance with the invention have the advantage, whilst distinguishing clearly trembling of the body from greater amplitude trembling phases due to unwanted vibrations, of showing up only the resting trembling, movements of the animal during the measurement having no effect on the result.
Stress in man is traditionally measured by measuring body temperature or cardiac rhythm. These parameters give only an approximate indication of the degree of stress, however, and devices available to the general public, in particular those which measure the temperature of the fingers by means of substances responsive to temperature, are highly inaccurate.
The device in accordance with the invention quantifies stress objectively and accurately using a physiological parameter different from those used previously: it quantifies the trembling of the organism when resting, which is invisible or virtually invisible to the naked eye in man. Measuring vibration of the human organism as a stress indicator is new as far as the applicants are aware. The present invention has the advantage of giving a more accurate result than previous devices which is more closely related to the actual degree of stress. The possibility of measuring stress using the present invention results from the fact that a stress reaction is accompanied by the discharge of adrenalin which increases the amplitude of nervous trembling.
Experiments have shown that vibration as measured using the device in accordance with the present invention increases effectively in persons in a stressful situation and in persons who smoke tobacco or consume unnatural foodstuffs, the level of trembling being then three to five times higher than under normal conditions. The measurement results decrease over a few days in persons who stop smoking, drinking coffee and/or adopt a more natural dietary regime Trembling also decreases between the start and the end of a relaxation session, which confirms that the measured parameter is a good stress indicator and opens up the possibility of using the invention to evaluate the efficacy of anti-stress methods (relaxation, seawater therapy, etc). At present there is no known means of reliably measuring stress and consequently no means of measuring the effectiveness of these methods or of comparing them with each other, as is now made possible by the invention. The inventors' experiments have shown that the smallest amount of unnatural substance (nicotine, cafeine, foodstuffs rendered unnatural by cooking or irradiation, bread, etc) when introduced into a living organism increases almost immediately the vibration as measured by the device to be described, which makes it possible to detect even very small amounts of abnormal substances in foodstuffs.
Patent FR 2 577 791 discloses a process and a device for evaluating the psychotropic effects of medication substances in animals by measuring meaningful agitation of the animals. The sensors and signal processing techniques of the present invention are very different from those as previously described in this French patent, however. In particular, the principle of measuring trembling when resting (treatment of the signal to ignore any signals other than low-amplitude signals, for example by detecting a minimum, ignoring unwanted signals of greater amplitude) is previously unknown, the prior art processes measuring all meaningful agitation of an animal and not its activity when resting.
Patent EU 0 087 015 describes a device designed to alert a farmer that a cow or other livestock animal is about to give birth. The device described detects contractions of the uterus of the animal by means of a mercury sensor which closes above a particular contraction threshold. This process is totally different from the present invention because the present invention measures the amplitude of trembling when resting, whereas the patent EU 0 087 015 measures muscular contractions above a particular movement threshold. The signal processing is therefore totally different: in the present invention, the amplitude of trembling when resting is measured instead of the muscular activity above a particular threshold, the muscle signal being eliminated because it is regarded as unwanted interference. Also, the sensor of the patent 0 087 015 produces a binary (on/off) signal which is obviously processed in a very different way from the signal of the present invention, signal.